1. Field of the Invention
The present invention relates to food temperature responsive control apparatus. More particularly, the invention relates to oven control apparatus including a temperature-sensing thermistor which may be included in a probe adapted for insertion into food being cooked in either a conventional or a microwave oven.
2. Description of the Prior Art
Prior art temperature monitoring devices, such as that disclosed in U.S. Pat. No. 3,815,114 -- Welch, assigned to the same assignee as the present invention, have provided for sounding an audible alarm or for de-energizing a heating means in an oven when food temperature, as sensed by a thermistor included in a probe inserted into the food, reaches a preset temperature. As used herein, "heating means" refers either to a resistance heater or a gas burner as in a conventional oven, or to a source of microwave energy, as in a microwave oven. Certain of the prior art temperature monitoring devices include means for performing various of the following functions in addition to means for performing the function of producing a signal for sounding an alarm or de-energizing a heating means; protecting against an open-circuited or a short-circuited condition in a circuit including the thermistor, guarding against responding to transient electrical noise and prematurely causing the heating means to be de-energized in response thereto, and latching the heating means in a de-energized condition, until manually reset, once the heating means has been de-energized. However, no prior art device combines all these functions in a simple and effective manner. Additionally, some of the prior art devices, if the thermistor has a non-linear temperature versus voltage characteristic and a linear temperature presetting scale is desired, require that either a non-linear potentiometer or a nonlinear temperature presetting scale be included in a temperature presetting means.